Ground loop measurement clamps of this type are already known. The general problem of these clamps is to have a pressure as large as possible for closing both of these clamps on each other in order to minimize the air gap between the contact faces of both jaws. In order to attain this goal, the clamps are designed so as to require a very large force for opening the jaws, which is very bothersome for the user. This force is located around 60 Newtons upon starting the opening and reaches 140 Newtons when maintaining the clamp in the completely open condition. Indeed, the more the clamp is opened, the more the force increases.